Reports of sabotage and intoxicated astronauts upstaged the US space agency's announcement on Thursday that the teacher tapped 21 years ago to fly in space would finally blast off aboard a space shuttle on 7 August.

Instead of discussing teacher-astronaut Barbara Morgan and the upcoming construction mission to the International Space Station (ISS), Nasa managers were left to fence with reporters at the Kennedy Space Center in Florida.

Revelations abounded over suggestions that a non-critical computer was deliberately damaged and that a panel set up to investigate astronaut psychological heath had uncovered at least two instances where astronauts were so intoxicated before flying that their crewmates and flight surgeons said they posed a safety risk.

Though scandalous, neither issue will have any affect on Nasa's plans to launch its second mission of the year.

Love triangle

The sabotaged computer, which was reported to Nasa by the manufacturer, will be repaired and loaded into Endeavour for transport to the space station, said associate administrator for space operations, Bill Gerstenmaier.

Mr Gerstenmaier declined to discuss the psychologists' report, which is scheduled to be released at a press conference on Friday.

Lisa Nowak's arrest prompted Nasa's report

Nasa commissioned the panel to look at astronaut mental health issues in the wake of the arrest of astronaut Lisa Nowak for assaulting a woman she thought was a rival for the affection of another astronaut.

Both Capt Nowak and her former flame, shuttle pilot Bill Oefelein, have since been fired from the astronaut corps and returned to jobs in the Navy.

Capt Nowak's trial on battery and assault charges, which police say stem from an attack on Navy Cmdr Oefelein's girlfriend in a parking lot at Orlando airport, is scheduled to begin in September.

Teacher in Space

Mr Gerstenmaier said that he did not recall any astronaut ever having to be disciplined for intoxication on launch day nor any shuttle flight that was ever in danger due to an inebriated crewmember.

"I've never had any instances of that," he told reporters.

Nasa, meanwhile, is on track to launch shuttle Endeavour on its first mission since before the 2003 Columbia disaster.

The ship has had a major overhaul and was in good shape for launch, said shuttle manager Wayne Hale.

Over the years, I knew it was going to happen sometime... I just didn't know when

Barbara Morgan

The crew includes Ms Morgan, now 55, who originally trained as the backup for Christa McAuliffe, who was selected as Nasa's Teacher in Space.

McAuliffe and six astronauts were killed in 1986 aboard the shuttle Challenger when a leaky shuttle booster rocket triggered an explosion 73 seconds after lift-off.

After the incident, Nasa asked Ms Morgan to stay on as its Teacher in Space designee and pledged a shuttle flight to fulfil McAuliffe's educational agenda.

But the agency also banned civilians from flying in its spacecraft, which left Ms Morgan in a conundrum for more than a decade.

Her ticket to ride was paired with Nasa's decision to send former Mercury astronaut and retired Senator John Glenn back into orbit on the shuttle for a geriatrics research programme.

Before making the flight, however, Ms Morgan had to become a fully trained astronaut. She joined the corps in 1998.

"Over the years, I knew it was going to happen sometime," Morgan said. "I just didn't know when."

Role model

Nasa has set aside about six hours for educational outreach programmes for Morgan during the mission, which is scheduled to last up to two weeks.

She will spend most of her time in space operating the shuttle's robot arm and overseeing the transfer of 5,000 pounds (2,000kg) of cargo to and from the station.

Barbara Morgan has been waiting to go into space for years

"I don't have a teacher as a crewmember," her commander, Scott Kelly, said. "I have a crewmember who used to be a teacher."

That's not how Ms Morgan sees herself, however.

"I'm very excited about flying to space, doing the job of an astronaut, but flying as a teacher, with the eyes, ears, heart and mind of a teacher and experiencing that and being able to share that," she said.

Ms Morgan said she made the commitment to fly after the Challenger disaster - a commitment that was tested again when Nasa lost another seven astronauts aboard Columbia in 2003 - to set an example for children.

"We had school kids all over the world looking at adults and watching what adults do in a bad situation, and I felt it was really important to show them that adults do the right thing," Ms Morgan said.

"I've carried that with me ever since. I'm personally very excited about going into space, but that's not my motivation. I'm here because of that and because I'm a schoolteacher."